<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
  <meta charset="UTF-8">
  <title>JavaScript 赋值</title>
</head>
<body>

<h1>+= 运算符</h1>

<p id="demo"></p>

<script>
  var x=7;
  x+=8;
  document.getElementById("demo").innerHTML=x;
</script>
</body>
</html>